Superconductivity in higher titanium oxides

TL;DR

This paper reports the discovery of superconductivity in higher titanium oxides Ti4O7 and g-Ti3O5, with g-Ti3O5 achieving a transition temperature of 7.1 K, and discusses the underlying bipolaronic mechanism.

Contribution

It introduces superconductivity in simple titanium oxides with a detailed analysis of the mechanism, expanding the class of known oxide superconductors.

Findings

g-Ti3O5 has the highest Tc among simple-oxide superconductors at 7.1 K

Superconductivity arises from bipolaronic insulating states

Superconductivity observed in epitaxially tuned, off-stoichiometric thin films

Abstract

Recent renewal of the highest transition temperature in a conventional superconductor of the sulfer hydride attracts much attention to exploring simple compounds with the lighter elements, situated in unconventional conditions. We report the discovery of superconductivity in simple oxides of Ti4O7 and g-Ti3O5 in a thin-film form having deliberately tuned epitaxial structures and off-stoichiometry. These higher titanium oxides join in a class of simple-oxide superconductors, and g-Ti3O5 now holds the highest superconducting transition temperature of 7.1 kelvin among them. The mechanism behind the superconductivity is discussed on the basis of electrical measurements and theoretical predictions. We conclude that superconductivity arises from unstabilized bipolaronic insulating states.